Abstract
Hyperthermia potentiates the influence of CO2 on pulmonary ventilation (VE). It remains to be resolved how mean skin (TSK) and core temperatures contribute to elevated exercise ventilation response to CO2.PURPOSETo assess influences of TSK and end‐tidal CO2 (PETCO2) on the ventilatory equivalent for oxygen (VE/VO2) during exercise with a hyperthermic rectal temperature (TRE).HYPOTHESISDuring hyperthermia mean skin temperature will positively interact with PETCO2 in their influence on exercise ventilation.METHODSSix participants 1.78 ± 0.13 m (mean ± SD) in height, who weighed 74.7 ± 16.5 kg and were 24.3 ± 2.3 yrs of age performed three 1 h exercise trials on each of 2 days in a climatic chamber. For each exercise session conditions were maintained at an RH of 29.5 ± 8.9 % and ambient temperatures of one of 25, 30, or 35°C. This gave 3 significantly different TSK levels (F=15.8, p=0.001) between ~33 and ~36°C. In each trial the volunteer breathed eucapnic air for 5 min during rest before cycling on an ergometer at either ~50 W (normothermic TRE) or at ~150 W (hyperthermic TRE). Once TRE stabilized the volunteers breathed hypercapnic air twice for ~5 min with PETCO2 elevated to ~+4 and ~+8 mmHg.RESULTSIn the normothermic TRE condition there was a significant effect of PETCO2 (P<0.05) but no effect of TSK on ventilation. In the hyperthermic TRE condition for VE/VO2 there were main effects of TSK (F=4.0, p=0.06) and PETCO2 (F=13.2, p<0.0001) as well as a significant positive interaction (F=3.7, p=0.01) between TSK and PETCO2.CONCLUSIONDuring exercise with a steady state hyperthermic core temperature, skin temperatures and PETCO2 positively interact in their influence on exercise ventilation.Supported by NSERC, Canadian Foundation for Innovation.
Published Version
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